"should i put this as my aspirational or solid??"
I think you are misunderstanding how it works, or I am misunderstanding what you mean by "aspirational or solid". You apply to five unis. At the point where you apply, you don't list them in any order, they are just five unis. Then you see if you get any offers. If you do, you accept one as your "firm" and one as "insurance". Usually you pick your firm as a higher offer than the insurance. So IF UCL make you an offer, you can put that as your "firm" and then choose another lower offer for your insurance in case you don't make the grade UCL want. On results day you find out which you are going to.
So it's fine to apply to UCL, if you wanted to you could apply to five "aspirational" unis who ask for grades higher than you are predicted. But that's risky. You might not get any offers. Then you would have to add more unis one by one until you got one offer, so at that point (unless you want to risk ending up in Clearing if you don't make the grades) you would be wise to pick unis you are pretty sure you can make the grades for. The other risk - you get an offer for one of these five universities you aspire to, but don't make the grades and again end up in Clearing on results day because you have no insurance choice.
Better to choose at least one in the first five that you are confident will make you an offer that you can meet the grades for. Then worst case if that's the only one that makes you an offer you can just have that one as your firm choice, but possibly you will have an aspirational firm and a safe insurance.